// Spun AJAX Framework
// Copyright (C) 2008 Blake Hegerle
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Formality.FormalSystem
{
    public class BindingOperator : PrefixOperator
    {
        public BindingOperator(string Binder, Variable Variable, params Proposition[] Scopes)
            : base(Binder, new Proposition[] { Variable }.Concat(Scopes))
        {
            this.Quantifier = Binder;
            this.Variable = Variable;
            this.Scopes = Scopes;
        }

        public string Quantifier { get; private set; }
        public Variable Variable { get; private set; }
        public IEnumerable<Proposition> Scopes { get; private set; }

        #region Proposition overrides
        public override Inference? Matches(Proposition that, Substitution Substitution)
        {
            var Matches = base.Matches(that, Substitution);

            /* Check for variable capture. */

            Substitution.RemoveSubstitution(Variable);

            if (Substitution.Any(S => S.Second.Equals(Variable)))
                return null;

            return Matches;
        }
        #endregion

        #region Sentence overrides
        public override void Bind(Bindings Bindings, int Depth)
        {
            Depth++;

            Bindings = new Bindings(Bindings);

            Variable.BindingNumber = Depth;
            Bindings[Variable.Name] = Variable;

            base.Bind(Bindings, Depth);
        }

        public override bool Equals(Sentence Sentence)
        {
            return base.Equals(Sentence);
        }
        #endregion
    }
}
